What population size characterizes a megacity?

A megacity is defined as a very large city that has a population of ten million or more inhabitants. This classification is significant in urban studies and geography because megacities often experience unique challenges and opportunities related to their size, such as infrastructure demands, environmental concerns, and social issues. The threshold of ten million is an accepted standard used by various organizations, including the United Nations, to identify and study these urban areas.

The other population size thresholds presented, such as up to five million, fifteen million, or over twenty million, do not accurately define a megacity. Cities within those ranges may be sizable and important but do not meet the criteria established for megacity status. The focus on ten million ensures that the term "megacity" captures those urban centers that have reached a significant scale, highlighting the impacts of rapid urbanization and global demographic trends.